The present invention relates to heat exchangers. More specifically, the present invention relates to a heat exchanger that is electro-hydrodynamically enhanced.
In a typical heat exchanger, heat from a xe2x80x9chotxe2x80x9d fluid is transferred to, and carried away by, a coolant. The typical heat exchanger is made of metal, which facilitates the transfer of heat from the hot fluid to the coolant. A bar and plate type heat exchanger made of metal is described in U.S. Pat. No. 5,183,106, which is assigned to the assignee of the present invention.
Heat exchangers can also be made of composite materials. See, for example, U.S. Pat. No. 5,628,363, which describes a plate-fin heat exchanger made of, carbon composite. Such composite heat exchangers also facilitate the transfer of heat from the hot fluid to the coolant. However, composite heat exchangers have lower thermal stresses and better corrosion resistance than heat exchangers made of metal. Composite heat exchangers can also be fabricated into complex geometries more easily than metal heat exchangers. U.S. Pat. No. 5,628,363, also assigned to the assignee of the present invention, is incorporated herein by reference.
However, heat transfer efficiency of heat exchangers in general is limited by the thermal conductivity of their structural materials (e.g., metal, composite). Heat transfer efficiency is also limited by the convective coefficient of the fluids flowing through the heat exchanger.
Increasing the heat transfer efficiency would allow size and weight of the heat exchanger to be reduced. Smaller, lighter, more efficient heat exchangers would be able to remove more heat than larger, heavier, less efficient heat exchangers. In the aerospace industry, for example, it is extremely desirable to increase the efficiency and reduce the weight of heat exchangers used on board aircraft. Reducing the weight reduces fuel consumption. Reducing fuel consumption, in turn, reduces the cost of operating the aircraft.
The present invention can be regarded as a heat exchanger that can be electro-hydrodynamically enhanced to increase heat transfer efficiency. The heat exchanger includes a plurality of plates stacked in a substantially parallel spaced-apart relationship, and a plurality of spacers located between the plates. The spacers and the plates cooperate to define hot-side and cold-side passageways. The plates are thermally and electrically conductive, and the spacers are electrically non-conductive. Such a heat exchanger allows an electric field to be placed across the plates. Applying the electric field causes the heat exchanger to be electro-hydrodynamically enhanced.